Spin-polarized density functional calculations were carried out on Er and Er-O defects in crystalline Si. It was found that the interstitial site was favored but the diffusion barrier of Eri was only 1.9eV, and inevitably Eri formed complexes with impurities and intrinsic defects following post-implantation annealing. The Er formed many defects with O, and it was argued that optically inactive Er2Si2O7 precipitates coexisted alongside active Eri-On clusters. The latter were unstable when neutral and possess a range of second donor levels around Ec–0.1eV. It was suggested that those with either deep levels or very shallow ones were inefficient room-temperature optical centers. The Eri-O3 defect had a donor level and symmetry consistent with observations of the room-temperature luminescence intensity and low-temperature crystal-field splitting.

Electrical Activity of Er and Er-O Centers in Silicon. D.Prezzi, T.A.G.Eberlein, R.Jones, J.S.Filhol, J.Coutinho, M.J.Shaw, P.R.Briddon: Physical Review B, 2005, 71[24], 245203 (6pp)